Photo gallery: Pigweed resistance to glyphosate herbicide

Bill McCloskey, University of Arizona Extension weed scientist, confirms Palmer amaranth resistance to glyphosate (Roundup) herbicide in a Buckeye, Ariz., cotton field. This is Arizona’s first documented case of herbicide resistance. 2008 file photo.

A greenhouse trial conducted by weed scientist Bill McCloskey on glyphosate resistance to pigweed in cotton. Photo courtesy of Bill McCloskey

A single, large pigweed can produce up to 1.6 million seeds which can spread at least 1,000 feet in the field; significantly further in a cotton picker. Photo courtesy of Bill McCloskey

A pigweed towers above young cotton plants. Photo courtesy of Bill McCloskey